Book lovers received a fitting surprise on President’s Day: news that a treasure trove of books belonging to our nation’s most bibliophilic president had been found.

Washington University announced yesterday that 74 books representing 28 titles in its rare books collection were once part of Thomas Jefferson’s personal library. The books had been donated to the college by the son-in-law of Jefferson’s granddaughter early in the university’s founding in the 1850s, university officials said. With that discovery, the university has been elevated to the third-largest collection of Jefferson’s books, after the Library of Congress and the University of Virginia.

Those 74 books are just a fraction of the impressive library Jefferson amassed over his lifetime. Unbeknownst to many Americans, Jefferson was a fervent reader and a serious collector of books. “I cannot live without books,” he once wrote to John Adams, confessing to a “canine appetite for reading,” The New York Times reported.

Jefferson had multiple book collections, among them 6,700 books he sold to the Library of Congress in 1815 and another collection, known as his retirement library, that reached 1,600 books by the time he died on July 4, 1826.

The books discovered in Washington University most likely belong to that final collection, the retirement library. The least known of Jefferson’s collections, the retirement library leans heavily on classics rather than his typical political and legal tomes.

Jefferson’s heirs reluctantly sold the retirement collection at auction in 1829 to pay off his debts, and researchers have been trying to track them down ever since.

Endrina Tay and Ann Lucas Birle are two of those researcher-cum-detectives. A project manager for the Thomas Jefferson’s Libraries Project in Monticello, Ms. Tay is reconstructing Jefferson’s libraries in order to make his books available online. Since 2004, she has been sleuthing to find books in his collections, which she considers intellectual clues about what he read, from where he got his ideas, and what influenced him.

Researchers like Tay and Birle are especially excited by the prospect of marginalia in the latest find. Jefferson sometimes wrote in his books, enhancing the cultural value of the books significantly. He usually initialed his books as a means of conveying ownership. He also corrected typographical errors and sometimes wrote notes in the margins to comment or reflect on the prose. Such notes are a goldmine for researchers, providing valuable insights on Jefferson’s thought formation, intellectual reflections, and idea wells.

A volume of Plutarch’s “Lives,” which recounts biographies of famous ancient Greeks and Romans, had scraps of paper with Jefferson’s writing in it, reported The St. Louis Post-Dispatch.

“Our discovery provides an amazing and intimate look into Jefferson’s world. To find his handwritten notations is like peering over Jefferson’s shoulder to see his mind at work,” said Leslie Greene Bowman, president of Monticello and the Thomas Jefferson Foundation, to The St. Louis Post-Dispatch. “To uncover such a significant collection of Thomas Jefferson’s personal books is a breakthrough for scholars and ongoing research on Jefferson’s life.”